Symptoms

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Most canker sores are round or oval with a white or yellow center and a red border. They form inside your mouth — on or under your tongue, inside your cheeks or lips, at the base of your gums, or on your soft palate. You might notice a tingling or burning sensation a day or two before the sores actually appear.

There are several types of canker sores, including minor, major and herpetiform sores.

Minor canker sores

These most common canker sores:

Are usually small

Are oval shaped

Heal without scarring in one to two weeks

Major canker sores

These less common sores:

Are larger and deeper than minor canker sores

Have irregular edges

May take up to six weeks to heal and can leave extensive scarring

Herpetiform canker sores

These canker sores, which usually develop later in life:

Are pinpoint size

Often occur in clusters of 10 to 100 sores

Have irregular edges

Heal without scarring in one to two weeks

When to see a doctor

Consult your doctor if you experience:

Unusually large canker sores

Recurring sores, with new ones developing before old ones heal

Persistent sores, lasting three weeks or more

Sores that extend into the lips themselves (vermilion border)

Pain that you can't control with self-care measures

Extreme difficulty eating or drinking

High fever along with canker sores

See your dentist if you have sharp tooth surfaces or dental appliances that seem to trigger the sores.

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